Induction of Neuron-Specific Enolase Promoter and Neuronal Markers in Differentiated Mouse Bone Marrow Stromal Cells Yossef S. Levy, Doron Merims, Hanna Panet, Yael Barhum, Eldad Melamed, and Daniel Offen* Laboratory for Neurosciences, Felsenstein Medical Research Center, and the Department of Neurology, Rabin Medical Center-Beilinson Campus, Petach Tikva, The Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel Received March 27, 2003; Accepted May 20, 2003 Abstract Mesenchymal stem cells in the adult bone marrow are differentiated to connective tissue, muscle, bone, car- tilage, and fat cells. Recent studies in cultures, animal models, and humans demonstrated the plasticity of these cells and their capacity to express neuronal markers. However, questions were raised as to whether the neu- ronal phenotypes reflect transient changes or even fusion with neurons. In this study, we induced the differ- entiation of mouse stromal cells to neuron-like cells and observed the activation of the tissue-specific promoter of neuron-specific enolase (NSE). We used transgenic (Tg) mice that carry the antiapoptotic human bcl-2 gene, expressed only in neurons under the NSE promoter. Some previous studies have indicated that the transgene induces neuroprotection in various animal models of neurodegenerative diseases. We found that following induction, the mouse stromal cells demonstrate neuronal phenotype and express the neuronal marker, NeuN (neural nuclei protein). However, most of the stromal cells derived from the Tg mice, but not the wild type, also expressed human Bcl-2, as indicated by immunocytochemistry. Furthermore, these induced neuron-like cells were more resistant to cell death induced by dopamine. In conclusion, our experimental models showed that stromal cells might be induced to neuronal phenotypes and activate neuronal-specific promoters. Moreover, neurons targeted over expression of the human bcl-2 gene and provided high resistance against such apoptotic insults. This novel strategy reveals a new horizon in the improvement of gene therapy, based on stem cell trans- plantation in neurodegenerative diseases. Index Entries: Bone marrow stromal cells; Bcl-2; neuronal plasticity; neuron-specific enolase promoter. Journal of Molecular Neuroscience Copyright © 2003 Humana Press Inc. All rights of any nature whatsoever reserved. ISSN0895-8696/03/21:121–132/$25.00 Journal of Molecular Neuroscience 121 Volume 21, 2003 Background Specific populations of neurons are destroyed in certain neurodegenerative diseases (e.g., dopamin- ergic neurons of the substantia nigra in patients with Parkinson’s disease, lower motor neurons in amyotrophic lateral sclerosis). Treatment for these diseases, if available, is mainly symptomatic. Replacements of the degenerated neurons by potent fetal or stem cells have already been used in animal models and in Parkinsonian patients, but results have proved inconclusive (Freed et al., 2001; Kim et al., 2002). In recent years, there has been an increasing inter- est in adult bone marrow-derived stromal stem cells that support hematopoiesis. These mesenchymal stem cells differentiate into connective tissue, muscle, bone, cartilage, and fat cells (Prockop, 1997; Pittenger et al., 1999; Deans and Moseley, 2000). Evidence has accumulated that human, rat, and mouse bone marrow stromal (mBMS) cells can also be induced to differentiate to neuron-like cells in cultures ORIGINAL ARTICLE *Author to whom all correspondence and reprint requests should be addressed. E-mail: doffen@post.tau.ac.il